Basic Notions: Electric Current, Voltage and Resistance

ПЕТЕРБУРГСКИЙ ГОСУДАРСТВЕННЫЙ УНИВЕРСИТЕТ ПУТЕЙ СООБЩЕНИЯ императора Александра I

Кафедра «Иностранные языки»

Professional English

The English language course for senior students specializing in

Electrical Transport and Power Supply

Учебное пособие для студентов IV курса специальностей Электрический транспорт и Электроснабжение

Unit 1

Basic Notions: Electric Current, Voltage and Resistance

Electric current is a flow of electrons, forming electric charge. Electric current is measured in amperes or amps (A). Electrons are particles with a negative charge, attached to atoms. When an electric current flows through a conductor, the electrons move from one atom to another. If the number of electrons flowing through a conductor increases then the amperage or ampage (current) increases.

The amount of current (in amps) flowing through a circuit partly depends on the electromotive force (EMF) of the electrical supply. EMF is measured in volts (V) and is called voltage.

The amount of current also depends on electrical resistance. It is a measure (in ohms - Ώ) of how easily current can flow through the conductors and components in a circuit.

Materials with high resistance are called electrical insulators. Materials that are good insulators are used to insulate conductors. An example is plastic insulation around electric wires.

The amount of current required by an electrical appliance or devices depends on the power of the appliance. The power is expressed in watts (W).